Microstrip ring resonators are now used in bandpass filter applications to overcome the influence that parasitic components generated at short circuited points in resonators have on circuit losses and resonance frequencies. However, conventional microstrip ring resonator BPFs are commonly designed for control of the in-band response without regard for the location of the out-of-band zeroes. The selectivity of a ring BPF may be improved by an appropriate choice of the zeroes. Thus a need exists for a ring resonator wherein the location of the zeroes may be easily designed for.